The reason you'd want a pair of the GK Ultraphones (or the cheaper Vic Firth headphones) is that they're true isolating headphones. The GK's are Sony MDR-7506's housed in Peltor Shooter's muffs. When you wear them, they block any incoming sound from the outside, so you don't need to turn them up and can listen at a comfortable level. This is why I don't recommend regular 'home use" headphones for drum use. The chance of hearing damage goes way up.

Or you could get in-ear monitors, like Shure SE215's, which block outside sound out as well.

Just to weigh in another option.

I use the Shure SRH 440 headphones with the SRH 880 ear pads - Dennis (Audiotech) recommended these to me. They block out a lot of ambient noise (I haven't got the precise figures available right now) but they can be considered as highly-isolating headphones. I still sometimes wear hearing protection underneath them (in-ear plugs) purely because I am absolutely paranoid about hearing loss and I'm very sensitive to high SPLs. The Ultraphones are even more isolating and are essentially high-quality ear defenders with drivers installed.

The vast majority of 'consumer' grade headphones will not isolate sufficiently, even those with some passive noise-cancellation. Forget about Skull Candy, etc and go for a pair of headphones from a recognised audio manufacturer. Their websites tend to have very detailed specification lists for each individual model.